Construction characteristics of subway shield method
The video shows the construction characteristics of subway shield method. 1. Little impact on the surrounding environment. 2. High construction precision requirements. 3. Classification of the subway shield method.
1. Little impact on the surrounding environment
Most of the construction process of the shield method is located underground, which has little impact on the surrounding environment of the construction site and is very suitable for construction in an urban environment with dense buildings and frequent crowd activities. When the shield machine is used for subway tunnel construction, the construction activities are located below the ground, the noise generated during the construction process is very weak, and the vibration to the surrounding soil layer is also small, so it is not necessary to make special arrangements for the construction site along the line like other engineering constructions Arrangements have little impact on-ground activities, especially transportation, and the surrounding environment.
2. High construction precision requirements
Metro projects have high requirements for construction quality and project safety and reliability. In order to achieve this goal, construction accuracy must be strictly controlled during project construction. When using the shield machine for construction, due to the high precision of the segment of the shield machine, it is ensured that the construction error can be controlled within a very small range. In addition, when the shield machine is excavating, it can only move forward and cannot make a backward movement. Once the phenomenon of retreat occurs during the construction process, it will inevitably cause serious damage to the shield device, resulting in unpredictable consequences and seriously affecting the project. Progress and construction safety. In order to ensure construction safety, in the early stage of construction, construction personnel must make full preparations to prevent any phenomenon that may cause the shield machine to retreat.
3. Classification of the subway shield method
(1) Earth pressure balance shield
The basic principle of the earth pressure balance shield is: with the advancement of the shield, the soil cut by the rotary cutter head and entering the sealed cabin will pass through the screw conveyor installed in the sealed cabin and the sliding gate or screw on the excavation port. Soil-discharging mechanisms such as type funnels are used to discharge soil while maintaining a stable state of the excavation surface while pushing the shield forward.
The front end of the shield is also a full-section cutting cutter head, and there is a soil inlet of a long cylindrical screw conveyor at the center or lower part of the shield, and its outlet is outside the sealed cabin.
The so-called earth pressure balance means that the sealed cabin of the shield machine is always filled with the soil cut by the cutter head, and a certain pressure is maintained to balance the earth pressure on the excavation surface.
(2) Mud water shield and mud water pressurized balance shield
The mud-water pressure balance shield is a tunneling method that maintains the mud-water pressure to balance the external pressure acting on the excavation surface and at the same time advances forward. Therefore, it is necessary to control the mud-water pressure on the excavation surface and the earth pressure in the sealed cabin. As well as the amount of unearthed that is balanced with the amount of excavated soil, etc., carry out necessary detection and management. There are many auxiliary supporting equipment for the slurry shield. Firstly, there must be a set of automatic control and slurry conveying systems, and secondly, a set of slurry treatment systems, so the equipment cost of the slurry shield is relatively high. This is its main disadvantage, but on the other hand, auxiliary equipment such as sludge treatment systems can be reused and economically feasible.
(3) TBM construction method
The TBM in the general definition refers to the full-face rock tunnel boring machine, which takes the rock stratum as the excavation object, and is usually suitable for digging long tunnels in rock strata with medium to thick burial depth and medium to high strength. Currently, commonly used types are open hard rock road headers, single-shield road headers, and double-shield road headers.
1. Open TBM
2. Single Shield Hard Rock Tunneling Machine
3. Double shield hard rock tunnel boring machine
